The relative age effect (RAE) is the effects of differences between athletes born in the early compared to the later months of the year. This study investigated the presence of RAE among 306 age-group swimmers competing in the 2014 Malaysian Schools Sports Competition (MSSM). Participants’ birthdates were grouped according to four birth quartiles (Q1- Jan to Mar; Q2- Apr to June; Q3 – July to September; Q4 – October to December). Data analyzed using chi-squared goodness-of-fit showed there was a significant difference among overall male but not for the female swimmers. There was a presence of RAE in the U-12 and U-15 but none in the U-18 boys’ category. Further analyses on the medal winners showed no RAEs on both gender. Physical attributes of the male swimmers, especially the early adolescents are suggested to influence the relative age effects in swimming.